This invention relates generally to mortise locks, and more particularly to a mortise lock for use where a high level of security is desired.
A mortise lock is designed to fit into a mortised recess formed in the edge of a door which is opposite to the edge of the door that is hinged to the door frame. The mortise lock generally includes a rectangular housing, or case, which encloses the lock components. The principal lock component is a beveled latch bolt which projects beyond the edge of the door and into an opening in the door frame to latch the door in a closed position. The latch bolt is moveable to a retracted position inside the case to permit opening of the door by operation of a latch operator, such as a door knob or lever handle.
Mortise locks are typically configured so that the latch operators mounted on the inside and outside surfaces of the door can operate independently. The outside latch operator can either be rotated to retract the latch bolt, or locked against rotation to prevent retraction of the latch bolt. Preferably, the inside latch operator can always be rotated to retract the latch bolt. The locking of the outside latch operator is usually controlled by a manual actuator, such as, for example, push buttons or a pivoted toggle, which is exposed at the edge of the mortise lock near the latch. The manual actuator has an associated link within the mortise lock case which, in one position of the manual actuator, engages a moveable portion of the outside latch operator inside the lock case so as to prevent rotation of the latch operator. In a second position, the link disengages from the moveable portion thus permitting rotation of the outside latch operator. The inside latch operator is usually unaffected by the manipulation of the manual actuator and remains rotatable at all times.
Adjustments must be made to the mortise lock depending on whether the lock is mounted in a left-hand or right-hand door. A mortise lock mounted in a left-hand door must be rotated 180xc2x0 about a vertical axis for mounting in a right-hand door. Consequently, the latch bolt must also be rotated 180xc2x0 about a horizontal axis so that the beveled face of the latch faces the door-closing direction. In addition, the inside and outside latch operators of the left-hand door mounted lock become the outside and inside latch operators, respectively, of the right-hand door mounted lock. Therefore, a change must be made if the latch operator controlled by the locking mechanism happens to be the inside latch operator when the lock is installed.
The necessary adjustments to the mortise lock can be accomplished without opening the case. Typically, the latch bolt can be pulled partially out of the housing, usually against the force of a spring, rotated 180xc2x0 and then allowed to be pulled back into the housing by the spring. However, this arrangement can lead to tampering after the lock is installed since the latch bolt can be reversed even when the mortise lock is in the door, which would prevent the door from closing. Moreover, conventional mechanisms for reversing the operation of the locking mechanism are complicated and difficult to manipulate.
Further, some mortise lock applications require a high degree of security, including government buildings, banks, prisons and storage facilities, as well as other applications where a higher degree of security may be desired. The latter may include institutional settings such as schools, and in particular classrooms. A typical classroom function mortise lock includes a latch bolt operable by an inside or outside lever handle. The outside lever handle may be locked against rotation by a key-operated cylinder in the outside of the door. A significant problem with this arrangement is that the latch can only be locked from the outside. As a result, if a teacher inside the room wants to lock the door, she must open the door to operate the outside cylinder.
For the foregoing reasons, there is a need for a mortise lock for use in applications where a high degree of security is preferred. The new, high security mortise lock should be lockable from the inside of the door. The new lock should also conveniently handle high traffic use. Ideally, the high security mortise lock is reversible and the latch assembly for use in the lock includes a latch bolt that cannot be reversed after the lock is installed in a door. Reversal of the latch bolt for use with a door of the opposite hand should be easily accomplished in the field. Any corresponding changes in the locking mechanism during reversal to effect locking of the outside latch operator should also be uncomplicated. The new latch assembly and locking mechanism should be straightforward to manufacture and use.
Therefore, it is an object of the present invention to provide a high security mortise lock, particularly for use in institutional applications such as schools.
Another object of the present invention is to provide a high security mortise lock which can be locked from the inside of the door.
Still another object of the present invention is to provide a high security reversible mortise lock wherein the latch assembly cannot be reversed when the lock is installed on the door.
A further object of the present invention is to provide a new latch assembly and locking mechanism for a high security mortise lock which are simple to reverse in the field prior to installation in the door.
According to the present invention, a mortise lock includes a housing for a latch bolt and a deadbolt which are mounted in the housing for movement between a retracted position where the latch bolt and deadbolt are inside the housing and an extended position where a portion of the latch bolt and deadbolt extend from the housing. First means are provided for moving the deadbolt between the retracted and extended positions. Second means, including a moveable member in the housing, are provided for retracting both the latch bolt and the deadbolt. A blocking element is mounted in the housing for movement between a first position and a position where the blocking element prevents movement of the moveable member. A locking lever operatively connects the deadbolt and the blocking element so that when the deadbolt is extended the blocking element is automatically moved to the position blocking the moveable member. A latch lever operatively connects the deadbolt moving means and the locking lever when the blocking element is in the blocking position for moving the blocking element out of the blocking position by operation of the first moving means. The first deadbolt moving and latch retracting means may comprise a key-operated cylinder.
Also according to the present invention, a security mechanism for a mortise lock is provided. The mortise lock is of the type comprising a housing for accommodating the lock components including the security mechanism, a latch bolt and deadbolt mounted in the housing for movement relative to the housing between extended and retracted positions, first means for moving the deadbolt between the retracted and extended positions of the deadbolt, second means, including a moveable member, for moving the latch bolt and the deadbolt to the retracted position, a blocking element mounted in the housing for movement between a first position and a position where the blocking element prevents movement of the moveable member, and a locking lever operatively connecting the deadbolt and the blocking element so that when the deadbolt is moved from the retracted position to the extended position of the deadbolt element is moved to the blocking position. The security mechanism comprises an arm member integral with the locking lever and a latch lever which operatively interengages the first moving means and the arm member when the blocking element is in the second position of the blocking element and the deadbolt is in the retracted position of the deadbolt so that the blocking element is moveable to the first position by operation of the first moving means.
In accord with the present invention, a latch assembly comprises a latch bolt having a first portion adapted to project from an opening in the lock housing in an extended position of the latch bolt while a second portion of the latch bolt remains within the lock housing. The latch bolt is removable from the lock housing through the opening. A securing member inside the housing is releasably attached to the second portion of the latch bolt. The securing member comprises a securing element having a blocking surface and means for biasing the securing element and blocking surface into engagement with the second portion of the latch bolt for releasably securing the latch bolt to the moving member. The securing element further comprises a disengaging surface which when moved against the force of the biasing means releases the second portion of the latch bolt from the securing member so that the latch bolt may be removed from the lock housing.
In further accord with the present invention, a mortise lock of the type having a latch bolt normally projecting from the lock housing and means including a moveable member in the lock housing connected to a door knob or lever handle for moving the latch bolt to a retracted position in the housing, has a locking mechanism comprising a blocking element in the housing and means for moving the blocking element between a locked position and an unlocked position relative to the moveable member. The blocking element has an opening adapted to receive a portion of the moveable member when the blocking element is in the locked position for allowing the moveable member to move and the door knob or lever handle to rotate. A stop is removably positioned in the opening of the blocking element for preventing movement of the moveable member when the blocking element is in the locked position.
Also in accord with the present invention, a mortise lock comprises a housing and a latch bolt removably mounted in the housing through an opening in the housing. A securing member is disposed inside the housing for movement relative to the housing. The securing member comprises a securing element having a blocking surface and means for biasing the blocking surface into engagement with the latch bolt for releasably securing the latch bolt to the securing member. The securing element further comprises a surface which when pressed moves the securing element against the force of the biasing means for releasing the latch bolt from the securing member so that the latch bolt may be removed from the housing. The securing member is moveable between a first position where the latch bolt is inside the housing and a second position where a portion of the latch bolt projects through the opening in the housing. Means for moving the securing member to the first position are provided, including a moveable member in the housing. A blocking element is disposed in the housing and means are provided for moving the blocking element between a locked position and an unlocked position relative to the moveable member. A stop is removably attached to the blocking element and adapted in the locked position to prevent operation of the moveable member.
An important feature of the present invention is that a key-operated cylinder is provided on the inside of the door for moving the deadbolt and retracting the latch bolt. Thus, due to the operative connection between the latch lever and the blocking element, the lock may be locked from the inside of the door, which is particularly important in a classroom setting. Thus, the mortise lock of the present invention incorporates a deadbolt operation into a traditional classroom lock.
Another feature of the mortise lock is the releasing surface of the securing member is only accessible through the side walls of the mortise lock case. Therefore, latch bolt reversal must be performed before the lock is installed. Moreover, once the latch bolt is freed from the moveable member, the latch bolt can be completely removed from the lock housing, reversed and reinstalled. The blocking element and removable stop for locking the lock are also accessible through the side walls of the lock housing. Thus, repositioning of the stop in the blocking element is also accomplished before installation. Preferably, the stop is a threaded plug which is received in a threaded opening in the blocking element.
Further, reversal of the latch bolt and locking mechanism is simple to perform prior to installation of the lock. A screw driver is the only tool needed to release the latch bolt from the lock housing for reversal of the latch bolt and locking mechanism. Once the lock is installed in a door, the latch bolt cannot be reversed because the latch bolt cannot be removed from the lock. The lock must be removed from the door to perform the reversal process.